Automatic dimpling machine



April 15, 1952 H. R. FISCHER 2,592,672

AUTOMATIC DIMPLING MACHINE Filed Dec. 17, 1946 I 7 Sheets-Sheet 1ATTORNEY April 15, 1952 H. R. FISCHER AUTOMATIC DIMPLING MACHINE 7Sheets-Sheet 2 Filed Dec. 17, 1946 M a 2 m m MM W [W A %Y April 15, 1952H. R. FISCHER AUTOMATIC DIMPLING MACHINE 7 Shets-Sheet 3 Filed Dec. 1'7,1946 INVENTOR A/mneo e fizmm fl g :W M M ATTOIQNEY April 15, 1952 H. R.FISCHER 2,592,672?

AUTOMATIC DIMPLING MACHINE Filed Dec. 17, 1946 7 Sheets-Sheet 4 INVENTORfi WIGO 1e F/p cflse BY 7 ATTORNEY April 15, 1952 FISCHER 2,592,672

AUTOMATIC DIMPLING MACHINE Filed Dec. 17, 1946 '7 Sheets-Sheet 6 TlcllzZ o INVENTOR E film/5e.

ATTORNEY AUTOMATIC DIMPLING MACHINE Filed Dec. 17, 1946 7 Sheets-Sheet 7T1 :IJE:

BY WM Patented Apr. 15, 1952 AUTOMATIC DIMPLING MACHINE Howard B.Fischer, Detroit, Mich., assignor to Chicago Pneumatic Tool Company, NewYork, N. Y., a corporation of New Jersey Application December 1'7, 1946,Serial No. 716,736

14 Claims. 1

This invention relates to fluid actuated machines for dimpling sheetmetal and for similar industrial purposes, and particularly to controlmeans associated with such machines for automatically closing anelectric circuit to initiate the cycle of operations and forautomatically opening such circuit to promptly stop and reverse thecycle upon the completion of the dimpling or similar stroke.

The main object of the invention is to provide a machine forautomatically dimpling sheet metal or performing similar operations uponsheet metal wherein the entire cycle of operations is completed and thepunching element is returned to initial position preparatory for asecond cycle by the automatic performance of the machine, no actionbeing required by the operator other than to position a work piecemanually to initiate each cycle of operations.

Another object of this invention is to provide a fluid actuated machinefor dimpling sheet metal or performing similar operations thereonwherein a punch, visible to the operator, may be brought intoregistration with a pre-formed aperture in a work sheet by manualmovement by the operator, and thereby to initiate a cycle of operationsthat will be automatically completed and the punch returned to initialoperative position without any further action on the partof theoperator.

Another object of the invention is to provide such control means forautomatically initiating operations upon the manual positioning of awork sheet by the operator as part of a system wherein the machine,after performing the dimpling or like operation, is automaticallystopped and reversed by a solenoid controlled valve in response to adeflection of a portion of the body of the machine upon a predeterminedworkin pressure being applied to the work piece.

Another object of the invention is to provide control means for a sheetmetal dimpling machine or similar pressure device whereby the cycle ofoperations is automatically initiated by the mechanical closing of anelectric circuit by the dropping of an operative member of the machineinto a preformed hole in the work sheet upon the registration of thedimpling punch with such preformed hole by the manual movement thereofby the operator.

Another object is to provide a simple mechanical device in such amachine to lift the punch from the work sheet to a predeterminedposition in elevation upon the completion of a cycle of operations, andat a predetermined point of time rapidl return the punch by directmechanical action to a position on the work sheet where the operator mayimmediately initiate a second cycle of operations by manually moving awork sheet to a predetermined position.

Another object of the invention is to provide a latching mechanismassociated with the ram of a dimpling machine which, upon completion ofthe dimpling operation and on the return movement of the ram, will liftthe punch holder from the work but at a predetermined point in thereturn movement of the ram will automatically release the punch holderto re-position the punch upon the work sheet preparatory to theinitiation of a second cycle of operations by the manual movement of thework sheet by the operator.

Still another object is to provide such a latching mechanism tocooperate with spring means in the ram whereby the punch, upon thecompletion of the dimpling operation, will first be elevated byengagement of the latch with the punch holder upon the return movementof the ram and then automatically and rapidly returned to a positionupon the work sheet by the force of the spring, sufiicient time beingallowed, however, during the elevational movement and beforethe releaseof the latch, to permit the operator to shift the work sheet to adesired position for reception of the punch preparatory to theinitiation of a second cycle by the manual movement of the work sheet bythe operator.

Other objects and features of the invention will appear more clearlyfrom the following description taken in connection with the accompanyingdrawings and appended claims.

In the accompanying drawings:

Fig. 1 is a perspective view, from the left side,

anism shown in elevation and the position regu lating mechanism inlongitudinal section; v

Fig. 5 is an elevational view, from the right side, of the latchingmechanism on the ram in elvated position with the punch resting on awork sheet and the punch switch in open position-the 'the punch droppedinto a preformed hole in a work sheet, the switch being in closedposition instantly before the ram is operated into pressing position;

Fig. 7is an elevational view of the ram in pressing position at the endof the power stroke with the latch lowered into engagement with the uponthe elevation of the ram;

Fig. 8 is a longitudinal section along theline 8--8 in Fig. 6; r

Fig. 9 is a longitudinal section along the broken line 9-4! in Fig. 6;

Fig. 10 is a cross-sectionalong the line !3Hl in Fig. 6;

Fig. 11 is a bottom view from the line H-H in Fig. 5;

Fig; 12 is a schematic diagram of the electrical apparatus andconnections showing the parts in idle condition but ready for operation;

Fig. 13 is a diagram Similar to Fig. 12 showing the parts at the end ofthe power stroke and-immediately-before the opening of the deflectionswitch;

Fig. 14 is :a View, chiefly inlongit-udinal section, of the punch anddie upon the completion of the dimpling operation;

Fig. 15 is a section throughthe bracket plate at,

line l5.l,5 in Fig. 9 showingthe device for holding the stripper memberin operative position;

Fig. 16 isan elevational view of the die spring and adjusting apparatusin'Fig. .4;

Fig. 1-7 is a perspective view of the leaf spring and cam followermounted upon the switch box; Fig.1;8 is a perspective view of the punchswitch box before assembly; ifig. 19 is aplan lever; and 1 Fig. 20 isaside View, partly in section, of the solenoid valve lever.

. Figs. 1 ,anda are drawn to a relatively small scale; Fig. 3 to :alarger scale; 4 to a still largerrsca-le; and'F s '5 o 1 inc u ive, 15.16, and to an even larger scale. Fig. 14 is one larger scal t an anyotfi ure.

Referring still to the drawings, the dimpling machine; which is theillustrative embodiment of the invention, is generall indicated at 20 inFig.1 and comprises a base 2i, a columnar support 22, and arnore or ;1ess massive yoke 23 terminating at thefront of the machine in opposedjaws 24 and 25 which respectively carry a movble zd mp n pu c 0 set an as ry dimpling -die-;2 l. Power to actuate the, punch derives frompressure 'fiuid introduced into the machine throughan'entrance fixtureis from a hose line 29 connectedto an-appropriate outside source ofcompressed air. From the entrance fixture 28 the pressure fluid passesthrough an air line oiler 30 and a pressure regulator 3!;centrolled by aregulator screw =3 2,;past the pressure gauge SS, and thence up throughahose line 34 to the Valve housing -35. Referring now to Fig. 3,pressure fluid passes through a control valve 36 in the housing to driveforwardly a reciprocating pisview of the solenoid valve ton 31 withwhich are associated rollers 33 transmitting motion to camlevertfltoactuate the ram or set holder il downwardly onits power stroke. Ram 4|on itspower stroke-exerts-dimpling pres-v sure upon the punch holder 92which carriesthe viewed from the right 4E punch 25, and in coaction withthe stationary die 21 forms a dimple in a preformed hole of the worksheet. An electrical system, including a solenoid 43, functions, ashereinafter described,

shown in Figs. 6, '7 and 8. may drop upon the work sheet S and ridethereon until the operator shifts the sheet to register the punch with apreformed hole of the work sheet. When the punch is riding on the worksheet, as in Fig. 8, the machine is idle. When brought into registrationwith a preformed hole, as in Figs. 6 and '7, the punch is forced throughthe hole by a compression spring 44; and the punch holder 42, in movingdownwardly, automatically closes a micro-switch 35 (hereinafter referredto as punch switch) in the circuit, as later described, to energize thesolenoid 43 and thereby to open the control valve 36 to move the piston31 to actuate the ramdl upon its power stroke. The invention alsoincludes a latching mechanism, generally indicated at 58, mounted on theram as hereinafter more fully described, to reciprocate with the ram.The latching mechanism 45 functions to engage the punch holder 22 whenthe ram has completed its power stroke; and upon the return movement ofthe ram, the latch carries the punch holder with it to a predeterminedpoint at which the latch is cammed into unlocking position, ashereinafter more fully described,

and the punch holder is permitted to drop to the work sheet S to be inposition to initiate a new cycle of operation as soon as the operatorregisters the punch with another preformed hole.

In the illustrative embodiment two means are disclosed for stopping thepower stroke of the ram and reversing the operation. Such means are morefullydescribed in the copending application of HowardR. Fischer andJames A. Roberts, Serial No.,514,068, now abandoned. Briefly considered,and as best shown in Fig. .1, and diagrammatically in Figs. 12 and 13,one such means .cap-, tures relative movement between the jaw 2d and thedeflection plate i! to pivot the arm .59 to open switch in the circuitsupplying current to the solenoid control valve 36. Theheavy pressure ofthe dimpling operation forces jaws 24 and 2 5 slightly but measurablyapart within the elastic limit of the material of which the jaws iscomposed,preferably boiler plate steel. Deflection plate 4-! is rigidlysecured vby screws 38 to the lower jaw but rides free of the upper jaw.Consequentlyit is subjected to no such pressure and remains stationaryrelative to the lower jaw.

When, therefore, jaw 24 moves upwardly in response to the dimplingpressure upon the work piece, pivot 5|, which is mounted on the jaw,moves upwardly therewith carrying with it the lever 52. Since the plate41 remains stationary, the short actuating arm 53 of the lever ;5 2 willengage the trip member 5 5 of the deflection plate during such upwardmovement, and the relatively long upright arm 55 will swingcounterclockwise about the pivot 51 to open the switch 50 tode-energizethe solenoid 63 and thereby close the control valve 35.Spring means (not shown) returns thelever to initial position. Thesecond stopping meanscomes into action in the event that the piston 3.!runs to-the extreme forward end of the cylinder 1% without tripping thedefiection switch .50. When din pling operations are performed on thinsheets, for example, there may not be enough strain on the yoke tooperate the deflection pressure switch 58. In such case the piston 31will overrun and the roller 38 rotatably mounted on the block 56 willstrike the lower end of the lever 58. Pivoted lever 58, thus actuated bythe roller 38 at the end of the forward stroke of the piston 31, opensstop switch 59 in the switch housing 68 to break the circuit of thesolenoid 43 and thereby cause the control valve 36 to reverse. It isintended that the present invention shall form an improvement to adimpling or riveting machine or press which is already provided withsuch deflection and/or automatic stopping device or devices. In such anassembly, the end-of-stroke switch is provided primarily for use attimes when the machine has been. converted to a riveter, instead of adimpler. Its usual function is to enable the operator to predeterminedthe degree of approach of the rivet set toward the dolly, and hence theheight of the upset rivet, by adjusting the dolly relative to the yokeand by permitting the piston to run the full stroke. The full stroke ismade possible by disabling the deflection switch whenever the operatorelects to predetermine the height of the rivet rather than thecompressive force thereon.

The stationary dimpling die 21 is supported on an annular shoulder 6| ofthe adjusting screw member 62 and is located by a centralizingcylindrical extension 63 of said screw member. The

die has a central aperture 64 (Fig. 14) shaped to 66 has a radiallyextending retaining flange 68 1.

which is seated on an annular ledge 69 formed adjacent the upper face ofthe jaw 25. By turning screw 62 relative to sleeve 66, the height of die21 relative to jaw on yoke 23 may be regulated to accommodate sheetmetal of different thicknesses.

The adjusting screw member extends downwardly from and beyond the yokejaw and threadably carries the holder H of the ring spring 12. Ringspring 12 (Figs. 4 and 16) is mounted transversely in the slot 13 in theholder and is maintained in operative position by transmission blocks 14and 15 each of which is formed with an arcuate surface 16 to engage theperiphery of the ring spring. The arcuate surfaces have slightly largerradii than that of the ring spring. Extending longitudinally through theadjusting screw member and projecting beyond its ends is apush rod 11.The upper portion 18 (Fig. 14) of the push rod is of reduced diameterand extends through and beyond the die centralizer 63 formed at theupper end of the screw member 62. The upper terminus of the push rodsupports a compression block 19 which isarranged in the die boreadjacent thecentral aperture 80 of the die and is adapted to be actuateddownwardly by the edge of the sheet metal S being dimpled. Block 19functions to coin the edge of the dimple by applying thereto a reactiveforce transverse to the plane of sheet S tending to cause the metal toflow upwardly and fill up the sharp corner adjacent the punch on theupper surface of the sheet S Edge coining is a common expedient in thedimpling art for the primary purpose of setting up stresses at the edgeof the hole to 6 condition the metal to withstand greater stretch of thehole without radial cracking.

As the punch moves downwardly in performing the dimpling operation, apart of its force is absorbed by the stationary die and its supportingelements including the yoke jaw 25, and a part is transmitted to thecompression block 19 and thence to the push rod 11. Thelower end of thepush rod cooperates with the transmission block 14 which transmits thelatter part of such force to the ring spring 12 by which it is absorbed.This will result in the ring spring assuming a slightly ellipsoidalshape, allowance for which is made in the shaping of transmission blocksI4 and I5, as previously described. Arrangedbelow and in cooperationwith the lower transmission block 15 and mounted in the holder II is ascrew 8'2 for. the micrometric adjustment of the compression of ringspring I2, said screwhaving a graduated knob 83 thereon. By rotation ofthe screw 82 upwardly through the holder H, compression is appliedthrough the transmission block 15 to the ring spring and thence throughthe upper transmission block 14 to the push rod 11 and the compressionblock 19 whereby to predetermine the reactive force of block 19 againstthe edge of the dimple while coining the latter during the dimplingoperation. Near the upper end of the push rod a shoulder 84 is formed bythe reduced diameter of the push rod extension 18 to retain the rodagainst upward movement in response to the pressure of the ring springwhen the punch is elevated upon the completion of the dimplingoperation. It has been found that the resilient opposition of thecompression block 19 as transmitted to it by the push rod from the ringspring will operate most effectively to coin the edge of the dimple. Thearrangement of the ring spring and push rod to support the edge coiningblock is old per se; but the adaptation of such an idea in combinationwith other features is considered novel.

The upper jaw 24 has a complementary movable dimpling punch or set 26mounted in the punch holder 42 which is removably mounted in the ram orset holder 4| and is capable of being brought. down during operationtoward the stationary die. The ram 4| (Fig. 3) is slidably mounted forvertical movement in bore 85 in the upper jaw Hand is itself formed witha longitudinal bore 86 and a counterbore 81 at its lower portion.Counterbore 81 (Figs. 6 and 1) forms a socket for the shank 88 of thepunch holder 42 and also provides a housing for the spring 44 which ispreloaded under compression between the punch holder shank and theinternal shoulder 89 of the bore to urge the punch holder downwardly.The ram has radial bores 9| disposed in diametrically opposite positionstherein adapted to mount a cross pin member 92. Said cross pin 92extends through a longitudinal slot 93 in the shank 88 of the punchholder 42 thereby limiting the longitudinal movement of the punch holderin reference to the ram, and also projects through radial bores 94 inlatch body 95 of the latching mechanism 46 as will be hereinafter morefully described. Since the compression spring 44 urges the punch holderdownwardly, the punch holder. will normally tend to maintain itself inthe most downward position permitted by pin 92 in the cross slots 93.

.The ram 4| (Fi 3) is slidably mounted for vertical movement in a pairof spaced but aligned bushings 9B, 91 arranged in jaw bore 85. Bushing96, which is mounted with a forced fit in the bore 7 85, is formed witha radially extending retaining flange 98 which seats in the jaw, andbushing ans mounted with a forced fit in bore 85. A'key 99 is mounted ina transverse slot I Win the upper portion of the ram and projects intoakeyway IIJI in the bushing 96. Key 99 serves to hold the ram 4| againstrotation relative to the bushing 96, and since the bushing is securelyfixed to the yoke by a force flt,the ram will not rotate duringoperation. A retainer ring IE2 is secured to the ram approximatelymidway its "length and; engages with a compression spring I03 whichrests upon" the bushing 91. Spring I93 tends to raise the ram M towardits upper inactive position, and upon the return of the piston '31,after the powerstroke, the springwill force the ram upwardly'to itsinitialor inactive position. A suitable washer IIl I is disposedbetweenthe'spring I03 and the retainerring I92. I

Atits frontend, and as shown in Fig. 2, the upper jaw 24 f the yokeextends upwardly and cooperates with a pair of transverse bolts I95 (oneshown) in supporting an upper frame I96 thereon, said framebeinggenerally inverted U- shaped in cross section. The front end of theframe I96 is closed'by a plate I01. The rear end of the frame is boltedto a fluid drive cylinder I88 which contains a chamber I99 and which inturn'i's bolted to control valve housing 35. As

- shownin Fig. 3 operating cam lever 39 is pivoted at I II within theframe I06 and is provided with a nose I I2 making active'contact withthe upper endof the mm H and during operation serves to depress the ramtocooperate with the punch holder '42 to bring the movable punch '26 andthe stationary die 2'I'into coaction to form a dimple.

The cylinder chamber I99 contains the reciprocable piston 31' providedwith a hollow piston rod 3 extending slidably't hrough a seal H4 in thefront end' wall II5 of the cylinder, the forward end of the piston rodreceiving a'boss IIB forming an extension upon the forked roller block56 on which a'pair of rotatable rollers 38 are mounted one above theother. The lower roller rides upon the upper approximately straightsurface II'I of the cam lever 39 while theupper roller rolls along theunder surface of a rail I I3 secured within the top of the'upper frameI08. Rollers38 roll over each other thereby relieving the forked block56 of a largepart of the reaction which is transmitted from the camlever upwardly through the rollers to the rail Ila and yokefi An innerpiston rod I I9 is screwed atits forward end into the boss IIB of theroller -block"and passes through the piston at I2I. Onthe rear side ofthe pistonhead, rod

IIS has a portion I22 of increaseddi'ameter surrounded by a' sleeve I23retained in association therewith-by a nut I2e"s'crewed'on to aredue'edportion atthe rear end of said rod. Thus, if the piston is-in a rearwardposition, the roller block will also occupy a rearward withdrawnposition in which the lower roller engages in the curved recessedportion I25 ofthe' cam lever near the pivot I I I"thereoftherebyallowingthe cam lever to swing upward about the pivot to a highinclinedposition. When the roller block 65 is forced forwardby the forwardtravel ofthe piston 31;the rollers 5'8 engaging against the rail H9 andcam lever 39 will obviouslyswingthe lattendown to cause the ram 4I todescend to force the dimpling punch .26 into cooperation with thedimpling die 21.

At the beginning of the forward movement of the piston, (the lowerroller 38 will engage the lever and moves more slowly than at first butwith uniform mechanical advantage or speed ratio between the piston 31and the ram 4| The result is that the pressure on the dimple surface isuniform throughout the power stroke as long as the air pressure behindthe piston 3! is constant. Within limits, therefore, variations in thethickness of the metal sheets being operated on, with correspondingvariations in the length of the power stroke, will notalter the shape ofthe dimple or the intensity of the force applied thereto. r

In order to actuate the piston, as just indicated, and thereby the camlever and ram, pressure fluid is transmitted through control'valve 36,the fluid being introduced into the machine as heretoforedescribed. Avalve suitable-for the illustrative embodiment and operating ona reciprocable principle is shown in the'copendi ng application of Howard R.Fischer and James A. Roberts, supra, reference to which is made for amore complete description.

Such a'valve is raised and lowered in response to an electr c-"magneticcoil device or solenoid. The solenoid it-is supported'on aframe I25(Fig. '3) which is mounted on'control valve'houe ing 35 and securedthereto by bolts I 21' (one shown The'solenoid comprises acore were;

ciprocating in a coil I29 rigidly mounted upon frame IEB-and connectedby a conductor, as here'- inafter described, to a terminal box Iii-I Thevalve stem I32 is screw-threadedforreception of two spaced adjustingnutsI33 and I34) Above nut I33 the sides of the-valve stem I32 arfletttenedto f t a rectangular slot in a lever -I35 (see Figs. 19 and 20). Therear end of the lever is pivoted at I36 on frame I 25, and the front endhas a forked portion I31 engaging a horizontal pin I38 carried bysolenoid core I28 whereby the reciprocating movement of thecore causesthe lever to rock about its pivot. Lever I35 normally l rests on loweradjusting 'nut I33 and is maintained in contact therewith by acompressign spring I39 which encircles valve stem I 32' and which isinterposed between the lever and t h'e upper adjusting nut I34. The twoaajust 'st;

' and lever I35 whereason the returnstrokethe valve stem I32 is carrieddown by the lever I in contact with the lo'wer'" adjusting "nut' I33.

Downward movement oft'he valve stem I3 2 is aided by a secondcompression spring "hitsu'rrounding the lower end I42 of the valve'stem' l32' and extending between shoulder I 43 on the slee'v e memberIda and a "collar I45fpir'1ned'to'the "vane stem. The purpose ofthe'spring I39 is 'toprevent injury "to the valve seats l isldue" to"the inertia of thesolenoid core 128 and alsoto 'ob viate thenecessityofclose adjustments.

As previously indicated, means areprovided forv automatically initiatinga cycle of operations 13y the mechanical action or the ament-slee inclosing a switch in the circuit to the solenoid,

suchaction taking place when the operatorbrings' a preformed hole in.the work sneetmt regisa tion with the pilot of the punch. "Such meansincludes a body portion I48 rigidlyattached-to the upper jaw 24 by boltsI49. Body portion I48 is provided with slots II through which the boltsare disposed to permit vertical adjustment of the bracket in relation tothe jaw. Plate I52 is joined to the body portion I48 by means of a blockI53 welded therebetween and extends downwardly and substantiallyparallel to the body portion I48 to carry switch housing I54. Bodyportion I48 and plate I52 may, however, be made unitary, the welding ofthe two together by means of the joiner block I53 being only forsimplification of manufacture. Plate I52 is formed with recesses I55 toseat the attaching bolts I56; and slots I51 (Fig. 5) in plate I52through which bolts I56 are mounted provide for the vertical adjustmentof the housing on the plate. Bolts I56 serve also to attach the leverretainer member I58 to the switch box I54. Plate I52 has a cut-off edgeto provide a camming shoulder l59 (Figs. 5 and 7) and has a bore I6Iwithin which is secured the shank I62 of the stripper member I63. Thefunctions of the camming shoulder I59 and the stripper member I63 willbe hereinafter more fully described.

Referring to Figs. 9, 17 and 18, the switch housing I54 is made of sheetsteel, folded to the desired shape, and closely surrounds a block I69,the latter projecting beyond the open end of the housing. Mounted in theblock I54 is a pair of lugs I64 between which is secured a horizontalpin I65 from which depends the lever I66. Lever I66, as best shown inFig. 17, has riveted to its free end a furcated member I61 in which isjournaled a shaft to carry the roller I68. Said lever is maintained innormal position (as shown in Fig. 5) by the flange I69 on the retainermember I58 and by the switch button I1I on the microswitch 45 which ismounted in block I60. The lever and roller are of relatively lightweight and the switch button I1I is tensioned outwardly with sufficientforce to maintain the lever against the flange I69. Counterclockwisemovement (as viewed from the bracket side of the machine and in Figs. 5,6 and '7) to close the switch button is imparted to the lever throughthe roller I68 as actuated by the downward movement of the punch holder42, as hereinafter described.

Latching mechanism 45 has a U-shaped body 95 disposed to partiallyencircle the lower portion of the ram 4i. As shown in Fig. 10, thecurved portion I12 of the body 95 is in spaced relation to the ram 4Iand the sides thereof are in con tiguous relation to the ram. Body 95has a pair of bores 94 drilled therethrough in opposed relation andadapted to register with the apertures 9| in the walls of the ram 4i.Pin 92 is mounted to extend through the registered holes BI in the ram Mand through the holes 94 in the bodyof the latch member 45 so that thelatch member may swing or pivot thereon. Pin 92 also extends through thelongitudinal slot 93 in the shank 68 of the punch holder 42, aspreviously described. The outer ends of the pin are formed with'groovesI13 into which retaining snap rings I14 are disposed to maintain the pinagainst axial movement. In other words, the latch member 46 will movelongitudinally with the rain 4I but is pivotable thereon upon the pin92, whereas the punch holder 42 moves with the ram 4I but is alsoadapted to move longitudinally with reference thereto and independentlyhereof to the extent permitted by the slot 93 in the shank of the punchholder 42.

Thelatch body 95 is disposed so that a clearance space I15 is providedto allow for the tilting of the latch from the position shown in Fig. 6to the position shown in Fig. 7. It is to be noted that the lower edgeI16 of the U-shaped portion does not touch the tool holder 42 when intilted position. Latch body 95 is joined by a curved portion I11 todepending side portions I18 in each of which is a bayonet slot I19. Suchslots are disposed on diametrically opposite sides of the extension ofthe axis of the ram and are adapted to slidably receive the pins IBIprojecting from diametrically opposite positions on the punch holder 42.The depending portion I18 is formed with a projection or trip finger I92the upper portion of which has a cut-off or chamfered shoulder I83adapted to act as a camming surface in cooperation with the cammingshoulder I59.

Latch body 95 has a pair of small drilled holes I84 (Fig. 10) whichserve as anchor means for the terminals of the springs I85 of thetilting device generally indicated in Figs. 6 and 10 as I86. Tiltingdevice I86 comprises a pair of support members I61 welded together attheir central portions I88 and having angularly projecting flanges I89which form a saddle to seat the device against the ram 4 I. The supportmembers curve outwardly and rearwardly to form a pair of holding wingsI9I each of which is provided with a spring anchor hole I92. As bestshown in Fig. 10, springs I85 are anchored in the wings I9I and in theend portions of the body member 95, and are thereby adapted to exercisea pulling or tilting force upon the body of the latch with the pin 92 asa pivot.

The various electrical connections and instruments used, such asswitches and relays and the like, in their details are illustrated indiagrammatic form in Figs. 12 and 13. In both the foregoing figures, theparts, either simplified or modified in form, nonetheless are indicatedas far as possible by the same reference numbers as borne by thecorresponding actual parts in the other figures already described. Thefirst of these two diagrams shows the apparatus in initial conditionafter the main line switch I93 has been closed and the apparatus orsystem is ready for operation. Closing the switch I93 connects thesystem to a source of electromotive force, diagrammatically indicated bya battery I94, and closes a circuit I95 extending from said sourcethrough the winding of a relay I96 and through a relay armature I91 andback contact (or break contact) I98 to ground. When relay I96 becomesenergized, its armature I99 moves into engagement with a front contact(or make contact) 29I to connect'the grounded end of relay winding I96through armature I99, front contact 29!, and conductor 292 to a fixedcontact member 283 of the stop switch 59. A movable contact member 294of the stop switch is controlled by the end 265 of the stop switch lever58 pivoted at 206 to the upper rail member. 'Said movable contact member204 is connected to a fixed contact member 201 of deflectionswitch 50while the latter has a movable grounded contact member 298 controlled bythe upper arm 55 of the deflection switch trip lever 49.

The apparatus includes a shiftable foot-operated switch 299 forcontrolling operation. A depressible treadle 2 I I controls the movablecontact member 2I2, and when the operator depresses the treadle saidmovable contact member 2I2 is brought down into contact with the fixedcontact member 2I3 thereby directing current through the conductor 2I4to one side of the punch switch 45. When switch 45 is closed by 11 thedropping of the punch holder, current-is led through the conductor 2 I5to ground. Relay ZIS is thereby energized and armature I 9? associatedwith the relay is shifted away from the grounded back contact I93 intoactive engagement with the front contact ZI'I. This operation ofarmature I9! passes current from the source I94 through the conductor2I8 to the solenoid 43, the current also continuing through conductor2I9, contact member 2, armatures I91 and Ice, contact member 2GI,conductor 2E2 to and through stop switch 59 as well as deflection tripswitch 59 through conductor 220 to ground. It is to be noted that afterthe relay I96 is energized and the armature I99 moves into engagementwith contact 29L a grounding circuit is provided 202, switches 59 and56, contact member 288 and conductor 220 toground, and will remainenergized until either of switches 59 or 58 is opened. The solenoid,energized bythe current, instantly raises the core'I28 to its upperoperative position, thereby elevating the valve stem I32 and allowingpressure fluid from the supply passage to pass through the valve 36 intothe rear portion of cylinder chamber I09 to drive piston 3? forward fromthe position shown in Fig. 12 toward that of Fig. 13. It is apparentthat the foot treadle 2II must remain depressed for the machine tooperate and that whenever the operator permits the treadle to elevate,the sol noid circuit is broken at the relay contact ZII and the solenoidvalve 35 moves to, or remains in, its normal position. Similarly, whenthe deflection trip lever 49 or the stop lever 58, as the case may be,opens the circuit to the solenoid, the solenoid is deenergized, itsmagnetic field is extinguished, the

' valve stem I32 drops and reverses the pressure to drop to the worksheet, to be in position to initiate a new cycle of operation as soon asthe operator shifts the work sheet S so that a drilled hole registerswith the punch. It will be seen that de-energization of solenoid I95 byinterruption of the circuit through switch 56 or switch 59 "resultingfrom movement of deflection trip lever 49 or stop lever 58 respectively,resultsin the'movement of armature I99 back to its initial positionwhere it remains until armature I91 is caused to engage'back contactI98. The latter action or condition cannot occur until solenoid 2I5 isde-energized by circuit interruption through punch switch 45 orfoot-operated switch 269. It will be evident that once the solenoidvalve 3%: is shifted to non-operative or normal position by breaking ofthe contact in either switch 59 or switch 59, it will remain in suchposition even when the contact in either switch 58 'or switch 59 is ie-made, as long as, solenoid I 96 remains de-energized. 'Ihus solenoidvalve 3.6 cannot again be put into operative position until a newoperating cycle is brought about by operation of. foot switch 289 and/orswitch 45 1 l V p Reference is to be had to Figs. 1 and 2 for thearrangement or the electrical system in connection with the variousactual partsof the machine. Terminal switch box I31 is mounted on theyoke by suitable means and is connected with a source of electromotiveforce by conductors enclosed within conduit 22! controlled by switchI93. From, said switch box IBI connections are made bythe pairofconductors 218, 2I9 leading to the coil of. solenoid G3; the pair ofconductors 2 I 4 and 215 leading to. the punch switch 45; and the pairof. conductors 292 and 220 leading to theserially connected deflectiontrip switch 50 and end-ofstroke switchti; all of said conductors beingenclosed within suitable conduits. Another conduit 225, carryingsuitable conductors, extends from the-box I 3 I to the foot switch 269.

In operation, a work sheet, indicated on the drawings as S, containingpreformed holes which are to .be dimpled, is initially positioned torest upon the stationary dimplingdie 21, and the dimpling punch 26 ispermitted to rest upon theworksheet. The cycle of operations is thenbegun .bythe operator manualy shifting the work sheet until av preformedhole is brought into registration with the dimpling punch, at which timethe spring. 44 will force the punch holder 42 downwardly, independentlyof ram 4|, to advance the punch 26 partly through the preformed hole. Asthe punch holder moves downwardly, its shoulder 2251 (Figs. 6 and?)contacts the roller I68 forcing it inwardly thereby moving the springpressed lever I66 counterclockwise (as viewed fromthe, bracket side. ofthe machine) to actuate the. punch switch button I'II to close the punchswitch,- 45 to complete the operating circuit to energize the solenoid43 to shift the power unit controlvalve 36 to drive the piston 37forward. The ram II is then driven downwardly by the cam, lever 39 (Fig.3), and its lower end is moved toward the upper shoulder 23I of thepunch holder 42,.which at this time. is stationary. During suchmovement, the latch 95, which is mounted upon the projecting ends of thecross pin 92, moves downwardly with the ram and, although constantlyurged to pivot or swing inwardly by the tilting device I86, the latchmechanism remains in the Fig. 6 position. As the latch drops, the pinsI8I projecting from the punch holder 42 slide upwardly into the bayonetslots I79, until they reach the enlarged upper end thereof, whereuponthe latch, as shown in Fig. '7, will pivot under the tension of spring Ito cause the pins I8I punch to lock in the bayonet slots I19. At thesame time, the lower end of the ram 4I' is brought into engagement withthe shoulder 23I on the punch holder 42. Continued downward movement ofthe. ram is accompanied by movement of the punch holder to cause thepunch 25 to dimple the sheet metal S as shown in Fig. 14. V

As the dimpling pressure increases, the jaws 24 and 25 are graduallyforced apart under the strain of the force transmitted through die 21added to that transmitted through edge coining block I9, causing arelative movement between the upper jaw 24 and the stationary deflectionplate 4'I. This relative movement is utilized to actuate the deflectionlever arm 49 to open the switch 50 in the. solenoid circuit thereby toterminate the power stroke of the ram, as previously described. Undercertain circumstances switch 5S, instead of switch 56, is opened by thepivoted" leverBB and the power stroke of the ram is thus terminated. Ineither event, the opening of the switch opens the circuit to thesolenoid to stop the downward movement of the ram. The ram then movesupwardly as urged by spring 44.

Upon the elevating or return stroke of the ram 4|, in response to theexpansion spring H13, the latch 95 moves upwardly therewith carrying thepunch holder 42 by virtue of the engagement of the pins l 8| in theenlarged ends of bayonet slots I19. Near the end of such upward movementthe projection or trip finger I82 on the latch member contacts thebevelled corner or shoulder I59 on the bracket plate I52 and causes thelatch member 95 to be cammed outwardly to unlatch the bayonet lockwhereupon the punch holder 42, under the urging of the compressionspring 44, drops, independently of the ram 4|, so that the dimplingpunch will again ride upon the surface of the work sheet S, preparatoryto the beginning of a new cycle of operations.

It is obvious that upon the elevation of the ram and the punch holderthe work sheet must be shifted by the operator before the punch holderdrops back upon the releasing of the latch. If

for any reason the operator should fail to shift the work sheet, thepunch will drop back into the previously dimpled hole and a new cyclewill automatically begin. No damage will thus be incurred although therewill be a waste of time. However, ample time is provided in the intervalbetween the completion of the dimpling operation and the releasing ofthe latch to permit the operator to shift the work sheet. It should benoted also that so long as the punch rides upon the surface of the worksheet, the mechanism cannot operate and the machine is in idle position.This added factor of safety is of importance as a preventive against thestarting of the machine by the accidental closing of the foot switch.

When forming dimples in a very heavy work sheet, it has been found thatthe metal is sometimes pressed in so tightly on the punch as to preventthe extrication of the punch from the work sheet and that in such casethe work sheet will elevate with the ram and punch. Stripper member I63is therefore provided to force the sheet away from the punch upon theupward movement thereof. Said stripped member comprises a forked portion232 (Figs. 6 and 11) whose tangs 233 extend partially around the punchwith an allowance for operative clearance, and an upwardly extendingshank I62 which is mounted in the bore I61 in the bracket plate to whichit is secured by a set screw 234 controlled by wing nut 235; (see Fig.15). The shank I62 is formed with a fiat 236 against which the block23'! is clamped by the action of set screw 234. Block 231 has anangularly formed flat shoulder 238 and is threadably mounted upon theset screw 234. Upon forward rotation of the screw, block 23'! is drawnoutwardly so that its shoulder 238 will cooperate with the flat 236 onthe shank of the stripper to tightly secure the stripper in operativeposition.

Upon upward movement of the ram 4!, the punch 26, in case it is stuck inthe dimpled sheet S, pulls the sheet upwardly until the latter strikesthe stripper I53, which is immovable relative to the yoke jaw 24.Thereafter, the sheet is held stationary while the punch 26, which ismore firmly aflixed to the holder 42 than to the work S, continues torise until it releases itself from thesheet and permits .the latter todrop to its 14 normal position where it is supported on 21.

Although in the illustrative embodiment of the invention, the mechanismis shown as dimpling a single sheet, it has been found that stackedsheets may be simultaneously dimpled by the machine of the invention.Furthermore, the invention is not limited in its application to dimplingdies of the edge coining type as shown in Fig. 14, but is adaptable todies and forming tools generally for performing dimpling, punching,pressing, crimping, riveting and similar opera.- tions.

What is claimed is:

1. A press comprising a fixed die adapted to support a work piece, alongitudinally movable ram, a punch supporting member telescopicallyslidable in the ram and adapted during movement to bring a movable punchdown upon the work piece, a U-shaped yoke terminating in a pair ofspaced jaws formed to carry the fixed die in one jaw and to support themovable ram in the other law, said jaws being adapted to spread inrelation to each other within their elastic limit in reaction to thepressure applied by the operative parts in performing the pressingoperation, pressure fluid operated means for driving the ram toward thefixed die, spring means to return said ram to initial position, ashift-able fluid control valve for controlling the fiow of pressurefluid from a source of pressure fluid to a fluid operated means, anelectric circuit, electrically operated means associated with saidcircuit capable of shifting said control valve from an initial positionto an operative position in which said valve is eiTective to passpressure fluid in one direction to said fluid operated means and causethe latter to drive the ram toward the fixed die, a switch in saidcircuit disposed adjacent the punch supporting member, means associatedwith the punch supporting member adapted upon a predetermined motion ofsaid member toward the die to close said switch thereby to shift saidvalve to operative position to pass pressure fluid to actuate the ramtoward the die, a stationary member secured at one end to one jaw of theyoke and having its other end arranged adjacent the other jaw of theyoke, a second switch in the circuit, means controlling said secondswitch adapted for operation in response to a predetermined relativemovement between the spreading jaws and the stationary member to openthe switch to stop the power movement of the ram, electrical means insaid circuit for forestalling operation of said electrically operatedvalve control means to permit the spring means to return the ram toinitialposition, and a third switch in said circuit controllable by theoperator to initiate operation of said electrically operated valvecontrol means.

2'. A press comprising a fixed die adapted to support a work piece, alongitudinally movable ram, a punch supporting. member telescopicallyslidable in the ram and adapted during movement to bring a movable punchdown upon the die work piece, a U-shaped yoke terminating in a pair ofspaced jaws formed to carry the fixed die in one jaw and to support themovable ram in the other jaw, said jaws being adapted to spread inrelation to each other within their elastic limit in reaction to thepressure applied by the operative parts in performing the pressingoperation, pressure fluid operated means for actuating the ram towardthe fixed die, a fluid control valve, an electric circuit, electricallyoperated means capable of moving said control valve from an initialposition to an operative position in which said valve isefrective topass pressure fluid in one direction tosaid fluid operatedmeans to causethe latter to actuate the ram toward the fixedldie, a switch in thecircuit of the electrically operated valve shlfting. means disposedadjacent the punch supporting. member, press lever means to control saidswitch, means on the punch supporting tool adapted upon a predeterminedmovement of the tool toward the dieto actuate said press lever-means toclose said switch thereby to shift said valve to pass pressure fluid toactuate the ramtoward the die, a stationary member secured at one endthereof to one-jaw of said yoke and the other endterminating adjacent tothe other jaw of the yoke, means responsive to a predetermineddeflection of said yoke by expansion to stop operation of saidelectrically operated valve shifting means with consequent cessation ofmovement of the plunger and the movable punch toward the fixed die, andmeans to shift'said valve to initial position.

3. A press according to claim 2 in which the switch closingmeans-associated with the punch supporting member comprises a switchbox, switch control means on the box, apress lever-on the box adapted toactuate said control means, and a cam on the punch supporting memberadapted upon predetermined movement of said member toward the die tomove said lever to close said switch. H j

v 4. A'press according to claim 2, wherein the ram hasassociatedtherewith a latch adapted to look upon. the punch supportingmember when the ram is in extended operative position and to elevatesaid toolupon the return of the ram.

5. A press as in claim 2, wherein the ram has pivotally associatedtherewith a latch formed with at least one bayonet slot and thepunchsupporting member is provided with at least one pin arranged toengage a bayonet slot'when the ram "isin. lowered position thereby tolock the too-1 to the ram for elevation upon the return stroke of theram.

6. A press comprising a U-shaped yoke terminating in a pair of spacedjaws, a fixed die in one of said jaws, a hollow ram reciprocable in theother jaw and adapted to transmit pressure sufficient for a formingoperation in sheet metal, pressure fluid operated means for actuatingthe ram on its power stroke, a shift-able fluid control valve forcontrolling the ram actuating means, an electric circuit, electricallyoperated means in said circuit for shifting the control valve to openposition to transmit pressurefiuid to actuate the ram-onits'power'stroke, a switch in the circuit of the shifting means,.meansupon a jaw adjacent the ram for supporting said switch, a tool holderprovided with a longitudinally slotted shank and "adapted for slidablemounting in 'the'ram and forindependent move- 'ment' relative thereto,said tool holder having ar'portion adapted to act as a cam, a pinrigidly mounted transversely ofthe ram and projecting through the slotsof the shank of the tool holder, said pin being adapted to limit themovement of the tool holder with reference to the ram, spring'meanswithin the ram adapted to move the tool holder with reference to the ramand toward the die,the cammingportion of said tool holder uponmovement'being adapted to close the switch inthe electrically shiftingmeans circuit thereby to actuate the electrically operated means toshift the control valve to open 16 position, latoh'means associated withthe ram and adapted to raise the tool holder from the die upon theelevation of the ram, and stop means upon the switch supporting meansadaptedto move said latch means to release the toolholder for movementtoward the die.

7. A dimpling machine comprising a U-shaped yoke terminating in a pairof spaced jaws, a fixed die in one of said jaws, a dimpling tool, ahollow ram reciprocable in the other jaw adapted to carry said dimplingtool and to transmit pressure therethrough sufiicient to dimple apreformed hole in sheet metal, pressure fluid operated means foractuating the ram, a shift:- able fluid control valve for controllingthe ram actuating means, an electric circuit, electrically operatedmeans for shifting the control valve to open position thereby totransmit pressure fluid to actuate the ram, on its power stroke, aswitch in the circuit of the valve-shifting'means, a tool holder for thedirnpling tool provided with longitudinal slots and slidably mounted inthe ram, said holder being adapted for transmitting operating pressurefrom, thelram through the upon registration of the. dimpling tool with/a7 hole in a work piece to force the dimpling tool into said hole, andmeans upon the tool holder adapted upon a predetermined movement of the.tool holder toward the die to move thepress lever to actuate the switchto shift the control valve to open position thereby to stop furthermovement of the ram on itspower stroke.

8. A press comprising a u-shaped yoketerminating in a pair of spacedjaws, ache in one of said jaws, a ram reciprocable in the other jaw,pressure fluid operated means for actuating the ram toward the die,spring means within the jaw adapted to return the ram to initialposition upon the release of the pressure driving fluid, a shiftablefluid control valve for controlling the pressure fluid supplied to theram driving means, a solenoid forming part of the control valve adaptedupon energization to move the valve to direct the pressure fluid todrive the ram toward the die, an electric circuit, a switch in thecircuit supplying current to the solenoid, a tool holder slidablymounted in the ram, a forming tool carried in the tool holder, means onthe tool holder adapted to close said switch upon apredeterminedmovement of the tool holder toward the die, spring means within the ramadapted to move the tool holder toward the fixed die upon theregistration of the tool with a hole in a work piece thereby to closethe switch to drive the ram toward the die, means associated with theram to limit the movement of the tool holder in the direction of thedie,said last mentioned means comprising an electric switch adapted to beoperated by said ram actuating means to de-energize the solenoid, andmeans forming part of the tool holder adapted to transmit the. force ofthe ram through the tool to the die. 7

9. A metal working machine comprising a frame having opposed jaws forreception "ofa workpiece having preformed portions, a tool reciprocablycarried by one of said jaws for operating on the workpiece, a motor indriving relationship with said tool, an electromagnetic controller forsaid motor, a first switch having a pair of normally open contacts, saidtool having means responsive to alignment of a preformed portion withsaid tool to effect closure of said contacts, a second switch carried bysaid frame which is normally closed but which is opened upon applicationof overload forces to said jaws, a first circuit for connection with asource of electrical energy and including a winding of a first relay, anarmatureof a second relay, a first contact of said second relay, and agrounding connection, a second circuit for connection with saidelectrical source and including a winding of said second relay, 2,control switch, said first switch, and a grounding connection, and athird circuit for connection with said electrical source and includingsaid electromagnetic controller, a second contact of said second relay,the armature of said second relay, the armature of said first relay, acontact of said first relay, said second switch, and a groundingconnection, said third circuit being arranged to provide a time lagbetween opening of said second switch and reestablishment of the thirdcircuit which is dependent upon the openingand closing of said firstswitch, the armature of said first relay being biased away from thecontact thereof, while the armature of said second relay is biasedtoward the first contact thereof.

10, A metal working machine comprising a frame having opposed jaws forreception of a workpiece having preformed portions, a tool reciprocablycarried by one of said jaws for operating on the workpiece, a motor indriving relationship with said tool, an electromagnetic controller forsaid motor, a first switch having a pair of normally open contacts, saidtool having means responsive to alignment of a preformed portionwithsaid tool to effect closure of said contacts, a second switch carriedbysaid frame which is normally closed but which is open upon predeterminedtool movement, a first circuit for connection with a source ofelectrical energy and including a winding of a first relay, an armatureof a second relay, a first contact of said second relay, and a groundingconnection, a second circuit for connection with said electrical sourceand including a winding of said second relay, a control switch, saidfirst switch, and a grounding connection, and a third circuit forconnection with said electrical source and including saidelectromagnetic controller, a second contact of said second relay, thearmature of said second relay, the armature of said first relay, acontact of said first relay, said second switch, and a groundingconnection, said third circuit being arranged to provide a time lagbetween opening of said second switch and re-establishment of the thirdcircuit which is dependent upon the opening and closing of said firstswitch, the armature of said first relay being biased away from thecontact thereof, while the armature of said second relay is biasedtoward the first contact thereof.

11. A metal working machine comprising a frame having opposed jaws forreception of a workpiece having preformed portions, a tool reciprocablycarried by one of said jaws for operating on the workpiece, a motor indriving relationship with said tool, an electromagnetic controller forsaid motor, a first switch having a pair of normally open contacts, saidtool having means responsive to alignment of a preformed portion withsaid tool to effect closure of said contacts, a second switcharrangement carried by said frame and including a switch which isnormally closed but which is opened upon application of overload forcesto said jaws and second contact of said second relay, the armature ofsaid second relay, the armature of said first relay, a contact of saidfirst relay, said second switch arrangement, and a grounding connection,said third circuit being arranged to provide a time lag between openingof said second switch arrangement and re-establishment of the thirdcircuit which is dependent upon the opening and closing of said firstswitch, the armature of said first relay being biased away from thecontact thereof, while the armature of said second relay is biasedtoward the first contact thereof.

12. In a press for the dimpling of sheet material containing pre-formedholes, the combination comprising a frame having opposed jaws forreception of the sheet material, a dimpling tool reciprocably carried byone of said jaws for operating on said sheet material and including apilot member, fluid pressure actuated means for driving the dimplingtool toward the opposite jaw, a valve means for controlling fluidpressure flow, an electro-magnetic operator for said. valve means, afirst switch means having a pair of contacts closed by movement of saidpilot memher into one of the pre-formed holes, a second switch carriedby said frame which is normally closed but which is opened uponapplication of overload forces to said jaws, a first circuit forconnection with a source of electrical energy and including a winding ofa first relay, an armature of a second relay, a first contact of saidsecond relay, and a grounding connection, a second circuit forconnection with said electrical source and including a winding of saidsecond relay, a control switch, said first switch, and a groundingconnection, and a third circuit for connection with said electricalsource and including said electro-magnetic operator, a second contact ofsaid second relay, the armature of said second relay, the armature ofsaid first relay, a contact of the first relay, said second switch, anda grounding connection, said third circuit being arranged to provide atime lag between opening of said second switch and reestablishment ofthe third circuit which is dependent upon the opening and closing ofsaid first switch, the armature of said first relay being biased awayfrom the contact thereof, while the armature of said second relay isbiased toward the first contact thereof.

13. In a press for the dimpling of sheet material containing pre-formedholes, the combination comprising a frame having opposed jaws forreception of the sheet material, a dimpling tool reciprocably carried byone of said jaws for operating on said sheet material and ineludingapilot member,v fluid pressure actuated means for driving the diinplingtool toward the opposite jaw, a valve means for controlling fluidpressure flow, an electro-magnetic operator for saidvalve means, a,first switch'means having a pair of contacts closed by movement of saidpilot member into one of' the pre-formed holes, a second switch carriedby said frame which is. normally closed but which is' opened uponpre-determined tool movement, a first circuit for connectionwith asource of electrical energy and; including a winding of afirst relay, anarmature ofasecond relay, a first contact of said second relay, and agrounding connection, asecond circuit for connection with saidelectrical source and including a windingv of said second relay, acontrol switch, said first switch, and a grounding connection, and athirdrci'r'cuit forconnection withsaid electrical source and includingsaid electro-magnetic operator, a second contact of said second relay,the armature of said second relay, the armature of said first relay, acontact of said first relay, said second switch, and agroundingconnection, said third circuit being arranged to provide a time lagbetween opening of saidsecond switch and reestablishmentof the thirdcircuit which is dependent upon the openingandclosing of said firstswitch, the armature of said first. relay being biased away from thecontact thereof, while the armature of said second relay'is biasedtoward the first contact thereof. 7

14. In a press for the dimpli'ng of sheet material containing pre-formedholes, the combination comprising a frame having opposed jaws forreception of the sheet material; 'a dimpling tool reciprocably carriedby one of said jaws foroperating on said sheet material and including apilot member, fiuidpressure actuated means for drivingthe dimpling tooltoward the opposite jaw, a valve means for controlling fluid pressureflow, an electro-magnetic operator for said valve means, a firstswitch'means' having a pairiof contacts closed by movement of saidpilot'mem her into one of the pre-formed holes; a second switcharrangement carried" by saidirame and including a switch'which isnormally closedbutfl which is opened upon application of overload,,force to said jaws anda switch which is' normally closed butwhich isopened upon a predetermined tool movement, a first circuit forconnectionwith a source of electrical energy andincludingfl'awinding ofa first relay, an armature of a second relay, a first contact of saidsecond relayyand' a grounding connection, a second circuit forconnection with said electrical source and ineluding a winding ofsaidsecond relay, a 'control switch, said first switch, and a groundingconnection, and a 'third'circuit for" connectionwith said electricalsourceand including-said electro-magnetic' operator, a second 'contact'of said second relay, the armature of said second relay, the armature ofsaid first relay, a-con tact of said first relay, saidsecond'switcharrangement, and a grounding connection, said third circuit beingarranged to provide atime lag between opening of said second'switcharrangement and 1 re-establishment of the third circuit which isdependent upon the opening and i closing of said first switch, thearmature of said first relay being biased away from the con-'- tactthereof, while the armature of said second: relay isbiased toward thefirst contact thereof.

7 HOWARD R. FISCHER. REFERENCES CITED;

The following references are of record in'the file of this patent:

UNITED STATES PATENTS.

